Focus Question: What are rocks and what are they made of? Description/Background Information:     Geologists recognize three major groups of rocks, each classified by their method of formation. These three categories are igneous rocks, sedimentary rocks and metamorphic rocks. Each group contains a wide variety of individual rock types that differ from one another by either the chemical composition, rock texture (such as grain size, mineral alignment, etc.) or both.     Igneous rocks form from molten rock, or magma, that comes from sources below the earth's surface. As magma cools it begins to harden or crystallize, and igneous rocks form. If this process occurs at or near the earth's surface, the mineral crystals within the magma have little or no time to form, producing rocks with crystals that are invisible to the eye (referred to as extrusive or volcanic rocks). If the rocks cool slowly beneath the earth's surface, larger, visible mineral crystals develop (referred to as intrusive or plutonic rocks).     Sedimentary rocks form from sediments, fragments of older rocks and dead plants and animals that have broken down into smaller pieces through erosion and transportation of sediment. These types of sedimentary rocks are called clastic (rock fragment) sedimentary rocks. These pieces are then compressed and cemented together to form a rock during a process called lithification. Clastic sedimentary rocks are classified by the size of sediments that vary from large particles (cobbles and pebbles) to microscopic particles (clay). Clastic sedimentary rocks are usually stratified or layered, and often contain fossils. A second type of sedimentary rocks form as a result of precipitation of chemicals directly from water or as a result of biological processes. These are called chemical or biochemical sedimentary rocks.     Metamorphic rocks form from other rocks as well, but unlike sedimentary rocks, these rocks have been altered over time by heat and pressure. Metamorphic rocks form beneath the surface of the earth where temperature and pressure are higher and have the opportunity to modify the original rock. These rocks are classified by the arrangement of mineral crystals within the rock. If crystals have been compressed into layers or bands, the rocks are referred to as foliated. If the rocks show no presence of layering they are referred to as unfoliated. There are two general types of metamorphism. Contact metamorphism involves heating of rocks adjacent to large masses of magma during cooling. The release of heat during cooling results in zones of metamorphic rocks around the mass of igneous rocks with minerals indicative of high temperature adjacent to the contact and minerals indicative of lower temperature away from the contact. The second type of metamorphism is regional metamorphism and involves changes in rock minerals and textures over a large region. Regional metamorphism is associated with mountain building or injection of large amounts of magma. Other less common types of metamorphism include hydrothermal metamorphism, dynamic metamorphism and shock metamorphism.

The building blocks of rocks are minerals. Minerals have specific chemical and physical properties, distinguishing them from other minerals. Properties such as color, streak, hardness, crystal pattern, specific gravity and luster are important characteristics that geologists use to identify specific minerals.

Some common minerals:
calcite	gypsum	hematite
limonite	feldspar (orthoclase)	quartz

Mineral mining is a major industry in New Mexico although recently has suffered as mineral prices have dropped and foreign resources have become important imports. New Mexico is a leading producer of uranium, potash and perlite, as well as being a major producer of copper, gold, silver, molybdenum and zinc. Many of these mineral-bearing sites are found within intrusive igneous rock formations that contain large crystals, referred to as porphyries.

Resources/Activities: Why is a diamond so hard?     http://www.eecs.umich.edu/mathscience/funexperiments/agesubject/lessons/beakman/diamonds.html How do gemstones get their colors?     http://www.eecs.umich.edu/mathscience/funexperiments/agesubject/lessons/newton/gems11.html Rocks are made of minerals.     http://www.mii.org/pdfs/every/rocksare.pdf Mineral Information Institute     http://www.mii.org/teacherhelpers.html

Standards: Those content standards that apply to this activity.